SUSCEPTIBILITY TO HEPATIC OXIDATIVE STRESS IN RABBITS FED DIFFERENT ANIMAL AND PLANT FATS

Objective: This study was designed to determine the effect of diets en riched with plant and animal fats on oxidative stress and glutathione metabolism in rabbit liver tissues. This study was conducted to invest igate whether the type of dietary fat will impact fatty acid compositi on and oxidant/antioxidant status in tissues. Methods: Rabbits were fe d diets containing 2 g corn oil/100 g diet (low fat diet, LF) and LF s upplemented with 16 g/100 g diet of either corn oil (GO), CO with adde d cholesterol (CO + C), milk fat (MF), chicken fat (CF), beef tallow ( BT), or lard (L) for 30 days. After the feeding period, livers were an alyzed for total fatty acid composition, thiobarbituric acid reactive substances (TEARS), conjugated dienes, and reduced glutathione (GSH), as well as for activities of glutathione peroxidase (GP) and glutathio ne reductase (GR). Moreover, to fully determine the oxidative stabilit y and free radical trapping capacity, TEARS levels were measured after additional exposure of liver homogenates to 10 mM 2,2(1)-azo-bis-amid inopropane-hydrochloride (AAPH) for up to 21 hours. Results: CO and CF , but not saturated fats such as MF, increased liver conjugated diene and TEARS levels and decreased liver GSH levels and GP activity. In ti ssues additionally exposed to AAPH, the maximum oxidation, measured as TEARS, was reached between 6 and 7 hours of treatment, independent of dietary fat. In addition, there was a marked effect of AAPH on the ma ximum rate of TEARS formation with the following descending order: CO > CF > CO + C > L > MF > BT > LF. This high susceptibility to oxidativ e stress in liver tissues of rabbits fed the CO diet may be explained in part by the significant elevation in linoleic acid (18:2n-6). Discu ssion: There appears to be an inverse correlation between dietary far- mediated oxidative stress and antioxidant enzyme activities. The prese nt data suggest that high levels of dietary unsaturated fat should be avoided if oxidative stress is a critical issue in nutrition-related d iseases. In addition, these data support our hypothesis that diets ric h in MF provide a lipid environment with low susceptibility to oxidati ve stress.